Hydrocarbon reforming with platinum catalyst and regeneration system therefor



. 4, 1956 J. F. sNuGGs ETAL HYDROCARBON REFORMING WITH PLATINUM CATALYSTAND REGENERATION SYSTEM THEREFOR Filed April 9, 1953 United StatesPatent C) HYDRocARBoN REFoRMING wrrH PLATiNUM CATALYST AND REGENERATIONSYSTEM THEREFOR John F. Snuggs, Chicago, lll., and James A. Bock, CrownPoint, and Joseph E. Wolf, Hammond, Ind., assignors to Standard OilCompany, Chicago, Ill., a corporation of Indiana Application April 9,1953, Serial No. 347,635

17 Claims. `(Cl. 196-50) This invention relates to hydrocarbon reformingwith platinum catalyst and regeneration lsystem therefor andI itpertains more particularly to a regenerative system employing aplatinum-on-alumin'a catalyst for converting a low sulfur low octanenumber naphtha rich in naphythenes and paraflins for obtaining very highyields of very high octane number naphtha.

For the past ten years nap'htha has been reformed by the so-calledhydroforming process which employs a molybdena-on-alumina catalyst,processes of -this ty-pe being illustrated by U. S. 2,388,536,2,357,332, 2,357,365, etc. In recent years the so-called platformingprocess has been adopted by many renners, this process beingcharacterized by the use of a iiuorine containing platinumoil-aluminacatalyst atpressures of at least about Y500 p. s. i. g. `and beingnon-regenerative in that reactorsare"` on-stream for months and aftereach on-stream period the yspent catalyst is replaced by fresh catalyst.Although patents purporting to describe platinum catalyst reformingoperations such as U. S. 2,560,329 and 2,566,521 state that `theplatinum-containing catalyst can be regenerated by combustion ofcarbonaceous deposits therefrom, no

such proce-ss has heretofore been commercially developed.

because it was found that such regeneration did not bring the catalystback to its original state of activity and. that after each suchregeneration, catalyst activity declined more and more rapidly while atthe same time falling to lower and lower levels so that it was thebelief of those skilled in the art that a regenerative process could notsuccessfully be employed with platinum-containing catalysts. Theselectivity of catalyst-s regenerated by prior me-thods was also foundto fall off sharply `after a relatively short period of on-streamoperations. An object of our invention is to provide an improvedcata-lytic reforming system employing a platinum type catalyst whichwill enable the production from a given charging stock of larger. yieldsof a produc-t of given octane number (or substantially increased octanenumber fory a given yield) than is obtainable by platforming and `toprovide an improved method and means for regenerating and rejuvenating'such catalyst so that th-e system may operate continuously tor a much`longer perior of time without undue decline (or rate of decline) incatalyst activity or selec,

tivity, the catalyst after each rejuvenation step 'being returned notonly to its initial activity but being characterized by its initialselectivity and low rate of activity decline.

A further object of our invention is to provide an improved hydrocarbonreforming and -catalyst rejuvenation and regeneration system of maximumilexibility at minimum investment cost and characterized by minimumoperating expense. Other objects will be apparent as the detailed-description of the invention proceeds.

In our system we provide four reactors of which at least three areon-stream and one is an alternate reactor, a charging stock heater andtwo reheaters, lconnecting lines and valves for passing charging stockthrough the charging heater, a first on-stream reactor, the first re-ICC heater, a second on-stream reactor, the second reheater,

and a thirdy on-'stream reactor while the alternate reactor isundergoing regeneration and rejuvenation, a simple arrangement ofconnecting lines and valvesbeing provided for substituting saidalternate reactor for any one of the on-stream reactors when the latterrequire regeneration land rejuvenation. In sharp distinction from thehydroforrning technique, the reactors are on-stream for a relativelylong time period of twenty-four to forty-eight hours or more and thereactors do not necessarily undergo regeneration -in any particularsequence. In other words the tirst reactor may be alternately on-streamand regenerated for several cycles before it is necessary to cut out thesecond on-stream reactor for regeneration and the third on-streamreactor may require even less frequent regeneration than the secondon-stream reactor. The reactant Vilow 'through the system is always inthe series: first reactor, irst reheater, second reactor,second'reheater and third reactor. The alternate reactor merely takesthe place of 4one of the on-stream reactors when this is necessary ordesirable. While three of the reactors are lalways connected for seriesiiow operation, the alternate reactor is connected for paralleloperation with a selected one of the reactors in said series. Theconnection for parallel operation is advantageous since the alternatereactor may actually be operated in parallel with any selected reactorin the series at such'times that none of the reactors requireregeneration.

An important feature of our system is our method and means for bothregenerating land rejuvenat-ing the catalyst in the reactor during theperiod when it is not on-strearn. In hydroforming operations it was thepractice to employ depressuring and repressuring steps which are notessential in our system. In hydroforming processes it was merelynecesary to burn all carbonaceous material otf the catalyst, then reheatthe catalyst before reintroducing recycle hydrogen and again goingon-stream; our process, however, requires a' separate rejuvenationtechnique in which the catalyst, after substantially all carbon isremoved therefrom, is contacted with agas having a higher oxygen partialpressure than could be employed in the regeneration (carbon burning)step. For rejuvenation the -catalyst should be treated with a gas havingoxygen conversion temperature or about 950 F. to 1l00 F. for

a time sufficient to bring the catalyst substantially to its originalstate of activity, selectivity and rat-e of decline. Rejuvenation may beeffected at temperatures up to l200 F. or higher and a rejuvenationtemperature of the order of 1000 to l200 F. is even more effective forrejuvenatingcatalyst than lower Vtemperatures of the order of 950 F.;however, when rejuvenation is effected above l000 F. it is necessarythat the catalyst bed be cooled before returning on-stream in order toprevent overtreating'of the introduced charge with attendant cracking,carbon deposits and product degradation. n

Our invention provides a flue gas generator which serves severalfunctions: it generates flue gas for -stripping hydrov gen out of areactor (when recycle flue gas is not available), it provides a heat-erfor heating air to the temperatures required for rejuvenation during therejuvenation part of the cycle and it provides a burner for consumingoxygen fromrejuvenation gases so that the catalyst chamber may be tilledwith substantially oxygen-free flue gas before it is purged with hotrecycle hydrogen prior to again going on-stream.

During the regeneration step, when flue gas contain-` y ing a smallamount of oxygen is being passed through a bed of spent catalyst with aninlet temperature of the order of 700 to 800 F., a llame front orcombustion zone slowly' traverses the catalyst bed. The amount of oxygeny Patented Dec. 4, 1956` in the introducedl gas Yis controlled toprevent this combustion front from exceeding about 1250 F. and it ispreferably maintained at about 1050 to 1100 F. As the ame frontprogresses through the bed, the inletend of the bed becomes cooler,approaching the temperaturel of the inlet gases, and the outlet end ofthe bed gets hotter because of heat picked up by gases at the combustionzone. In our process we make provision for reversal of iiow during orbetween the regeneration, rejuvenation and ilue gas purging steps sothat the bed temperature may be maintained more nearly uniform and/or sothat gradual heating or cooling of the bed may proceed from either endthereof. This feature is useful in bringing the bed after each operationto the optimum temperature pattern desired in the next operation.

Since the gas recirculation in the regeneration-rejuvenation systemshould not be called upon to operate at temperatures above about 1050"F., preferably not above 850 F., any recycled flue gas is cooled to suchtemperature and since it is desired to employ a higher temperature inthe rejuvenation step, the additional heat is supplied by burning fuelin the flue gas generator.

The accompanying drawing, which forms a part of this specification, is aschematic flowsheet of a 9,000 barrel per day reforming plant embodyingour invention.

The following example of our invention is by way of illustration ratherthan limitation. In this example the naphtha charge is a 58.2 APIgravity Mid-Continent naphtha having an initial boiling point in ASTMdistillation of 120 F., a`10 percent point of about 175 F., a 90 percentpoint of about 340 F. and a maximum of about 410 F. The charge containsonly .05 weight percent sulfur and, in general, the sulfur contentshould be below about .l percent. The charge has a clear F-l octanenumber 46, F-2 octane number 45. The charge contains no olens, about 40percent naphthenes, 8 percent aromatics and 52 percent paraflins, all byvolume.

Such charge is introduced by pump and line 11 to heater 12 wherein thecharge is vaporized and heated to a temperature of about 950 F. at atransfer line pressure of about 220 p. s. i. g. Recycle hydrogen fromline 13 (or extraneous hydrogen from line 14) is introduced bycompresser 15 and line 16 to heater 17 wherein it is heated to atemperature of about 1050 F. at about 220 p. s. i. g. and the combinedstreams pass through transfer line 18 and inlet line 19 to reactor 20,valve 19a being open and valve 19a being closed. Reactor 20 containsabout 10 tons of platinum-on-alumina catalyst in the form of oneeighthinch pills, the bulk density of the catalyst being about 60 pounds percubic foot. The catalyst is preferably one which has been prepared bycontacting an aqueous solution of chloroplatinic acid containing fromabout 3.5 grams of platinum per liter with an ammonium suldesolubilizing agent for converting the platinum into a solubilized formof platinum sulde in a stable aqueous solution, then combining this trueor colloidal solution with hydrous alumina prepared as taught in U. S.Reissue 22,196, the relative amounts of the two components being such asto produce a final catalyst containing about .3 to .5 percent or more ofplatinum by weight on a dry A1203 basis, the resulting mixture beingthen dried and calcined. The alumina may contain up to approximately 1percent by weight of fluorine (although it is preferably uorine-free)and it may contain a small amount of titania but it should besubstantially free from sodium, iron and molybdenum oxides since thelatter have been found to poison the resulting catalyst. Other methodsof preparing the alumina base may be employed but best results areobtained by using an alumina of the highest purity obtainable. Alsoother methods may be4 employed forincorporating the platinum but sincethese form no part of the present invention, they will not be describedin further detail.

The dried and calcined catalyst in the reactor has previously beenbrought to reaction temperature and pressure bythe circulation of a hothydrocarbon aud/ or hydrogen gas therethrough, and if a hydrocarbon gasis employed for heating purposes, it is preferably purged from thesystem before the heated charging stock is introduced. The mixture ofhot charging stock and hydrogen (the latter usually being la recycledgas containing about 80 to 90 Ymol percent hydrogen and employed at therate of about 1,000 to 8,000, e. g. 4,000 standard cubic feet per barrelof charge) is introduced into reactor 20 at about 980 F. Due to theendothermic nature of the reaction, the partially converted charge is ata temperature of about 860 F. when it leaves the reactor 20 through line21 (valve 21a being open) which leads to rst reheater 22 wherein thepartially converted charge is brought back to a temperature of about 980F. It is then introduced by line 23 and inlet line 24 (valve 24a beingopen and valve 24a being closed) to reactor 25 at an inlet pressure ofabout 200 p. s. i. g. Reactor 25 contains the same amount of the sametype of catalyst as employed in reactor 20 and here again the reactionis endothermic, the partially converted charge at a temperature of about900 F. being passed through line 26 (valve 26a being open) which leadsto second reheater 27 wherein the partially converted charge is broughtback to a temperature of about 980 F. It is then introduced by line 28and inlet line 29 (valve 29a being opened and valve 29a being closed) tothe third reactor 30 which likewise contains the same amount of the sametype of catalyst as employed in the prior reactors. Due to pressure dropin reactor 25, heater,27,etc. the inlet pressure to reactor 30 will beabout 190 p. s. i. g. The final product stream leaves reactor` 30through line 31 (valvela being open) and line 32 to gas separation andproduct fractionation systern 33. Y

In system 33 a recycle hydrogen stream is separated from condensedliquids, e. g. at about 170 p. s. i. g. and 105 F., Vthe condensedliquid is fractionated and/ or de- `propanized, the net gas productionbeing withdrawn through line 34 and the reformed naphtha or gasolinebeing withdrawn through line 35. Any higher boiling material or polymeris withdrawn through line 35. That portion of the .separated hydrogenstream which is rev quired for recycle is withdrawn through line 13 ashereinabove described. Since no invention is claimed in the gasseparation or product fractionation system per se, it is unnecessary todescribe it in any further detail.

After the system has been on-stream for one or more days there will be adecline in activity of the catalyst particularly in lead reactor 20. Theextent to which product octane number falls off may be minimized byincreasing the charge inlet temperatures to one or more of the reactorsor decreasing the charge rate but with the 200 p. s. i. naphthaconversion in the presence of platinumon-alumina catalyst maximum yieldoctane number relationships are obtained by periodically regeneratingand rejuvenating the catalyst. The lead reactor may require suchregeneration and rejuvenation more frequently than the final reactor andwe have provided asystem in which an alternate reactor 36 may take theplace of any one of the on-stream reactors 20, 25 and 30 by a remarkablysimple arrangement of valves and connections. Thus after about a day ortwo on-stream the fresh catalyst in alternate reactor 36 may be broughtto conversion temperature (as hereinabove described), valves 41a, 40a,37a and 19a' are opened (40a being closed) so that the introduced chargemay flow through line 37 to reactor 36 and valve 19a is closed. It willbe observed that immediately prior to the closing of valve 19a, reactors20 and 36 are, in fact, operating in parallel, both receiving preheatedcharge and hydrogen from line 18 and both discharging to the inlet ofpreheater 22. To displace or purge hydrocarbons from reactor 20 aftervalve 19a has been closed, hot recycle hydrogen from lines 38 and 39 isintroduced to reactor 20 by opening valve 39a. When the purging ofreactor 20 is complete, valves 39a heater is now coming from reactor 36through lines 40- and 41, valves 40a and 41a being open andvalve 40abeing closed.

In a similar manner alternate reactor 36 can take the place of reactor25 by opening valves 24a and 42a and closing valves 24a, 26a, 19a and41a. Alternate reactor 36 may take the place of reactor 30 by openingvalves 29a and 40a and closing valves 29a, 31a, 24aV and 42a. It will benoted that reactors 25- and 30 are connected for parallel operation withalternate reactor 36 and such parallel operations with either of thesereactors may, Of course, be continued during any period when none of isopened and valve 63a maybe closed sincethe desired cooling may now beelfected by gas which is recycled tinued while the introduction of fueland air to vessel 59 the catalyst in the system requires regeneration.The

hydrogen purge of reactor 36 is effected by opening valve 43a in line43, the purging of reactor y25` is effected by opening valve 44a in line44, and the purging of reactor 30 is effected by openinglvalve 45ainline 45. The vhot hydrogen for effecting such purging steps may be aportion of such re'cycle hydrogen which does not pass through heater 17or it may be a part of the recycled hydrogen which has passed throughonly a part of the heating coils in heater 17 (as shown).

Referring next to the regeneration and rejuvenation system, we providean upper regeneration gas line 46 with connections 47, 48, 49 and 50 toreactors 36, 20, 25 and 30 respectively. i Similarly we provide a bottomregeneration gas line 51 with' connections 52, 53, 54 and 55 to reactors36, 20, 25 and 30 respectively. Each of the regeneration gas connectinglines leading to a reactoris provided with a valve designated'by theconnection line` reference character followed by fr, e. g. 47ay 48.11.In connections leading to on-streamreactors .these valves are, ofcourse, closed. Y l i l Air for flue gas preparation, regeneration andrejuvenation is supplied from source 56 ,by compresser57 whichcompresses it to a pressure up to L about 220` p. s. i. g. Thecompressed air may be introduced ,through line 58 and valve 58a to adownstream portion or secondary combustion area of flue gas generator 59and/or the compressed air or portion thereof may be introduced throughline 60 in valve 60a to: the inlet'end or primary combustion area of theflue gas ygenerator along with fuel gas introduced by compresser f61from sourcer6r2. A pilot flame or other ignition device (not shown) isprovided in theprimary combustion zone and the proportion of fuel gasintroduced by compresser 61 to air introduced by line 60 is controlledto give eicient combustion. During start up operations all air isintroduced `through line `60 for generation ofy fluefgaswhichrleaveslvessel 59 through line 63 (valve`63a being open andv valve7, 1a y being closed) through. heat exchanger 64 wherein the `ue gas iscooled to about 850 F. by. water from line 65ifor generation of steamwhich isidischarged by line 66'to Vsep-s arator 67, the net steamproduction .beingml discharged through line 68 (waterinlet notzshown):AThe cooled Y flue gas inrreturned by circulating compresser 69 and line'70 to flue was generator `59this ,operationubeing `continued till thepressure `in the ilue gas generator reaches approximately 220 p. s. i.gaat which timel the temperaj ture of the flue gas due to circulationthrough the cooler will not substantially exceed about 850 F. i Y r Atthis stage valve 71a is openediandrthe fluegas is passed by line 71through three-way valve 72 and `lines 73, 46 and 48 to the top ofreactor 20 (assuming that this reactor is to undergo regeneration andthat valves 19a, 39a and 21a are closed). Theflue gas flows downwardlythrough the reactor and purges `out l'iydrogen,l the i purged gas beingwithdrawn through lines U53 (valves 53a aand 48a being open), 51 and 74Vthrough three-way valve Y 7S to line 76 (valve 76a Vbeing'open) to line-77. until n the pressure` in line 77 is Alsuiiicient to operi valve'18a which maybe set to open at about 210 p. s.i. g,j-for venting gasesthrough- `line 78. Hencethepressure in line 77V thus reaches thedesired.operating:.pressurerwYalve77ar is substantially eliminated sothat the temperature of the catalyst bed in reactor `20 is not onlypurged from hydrogen but is brought to a temperature of about 850 F. Atthis stage a small amount of air is introduced into the circulatingstream in amounts controlled by valve 58a to initiate combustionofcarbonaceous deposits on the catalyst, the amount of introduced airbeing controlled to prevent the combustion front from substantially ex--ceeding abouty l050 F. The combustion front thus slowly traverses thereactor bed, the net volume of produced gases being vented through line78 and the circulating stream being cooled to a temperature in the rangeof about 700 to 850 F. by heat exchanger 64. When the combustion fronthas completely traversed the bed the catalyst is fully regenerated inthat all carbonaceous deposits have been burned and most of the bed isat a temperature not substantially higher than about 850 F. Thecirculating stream during Vregeneration has an oxygen partial pressurenot substantially exceeding .3 atmosphere s (i. e. about 2 percentoxygen in recirculating flue gas).

While the regeneration of platinum type catalyst will bring itsselectivity and activity substantially back to its original level,regeneration alone is not adequate because after long periods on-streamit is found that activity falls v01T at much more rapid vrates and thatthere is a sharp increase in selectivity decline.l In order to maintainthe catalyst at high `activity and selectivity, to vprevent an undulyrapid rate of activity decline and to insure against any lossV inyield-octane number relationship we next effect a rejuvenation of thecatalyst. This rejuvenation is effected by increasing the oxygen partialpressure ofthe circulating gas to at least .4 atmosphere and preferablyto about l to 4 atmospheres and increasing the temperature of thecatalyst bed to at least reaction temperature and preferably lto atempera-ture of about v950 to 1200 F., e. g. l050 F. At this stagesuiiicient fuel gas is introduced into vessel 5-9 with the requiredamount of air through line to markedly increase the temperature of thecirculating gas stream and additional air isintroduced through line 58to markedly increase the oxygen partial pressure in the circulatingstream. For best results valve 77a is closed and a hot compressed air ispassed through the catalyst bed diluted with only the amount of flue gaswhich is produced by the necessary combustion of fuell toV heat thecompressed air to the rejuvenation temperature. compressed air may beeliminated by provision of a fired indirect 4air heater but usuallyVthis separate equipment is unnecessary in 200 p. s. i. g. operationssince the vamount of ilue gas dilution in the air heating step does nott lower the oxygen partial pressure below operable limits.

The passagel of hot compressed air through the catalyst bed ispreferably' continued until the entirejbed tem# Y perature is elevatedto above 950 F. andfris preferablyv yelevated to about 1050" F. When thebed temperature reaches thistlevel the rate of heated compressed air inbeenon-stream. A"catalystwhich is 50 percent deacti`v vated-requires amuch longer time than a catalyst which is only `5to Vl0 percent..deactivated. For relatively fresh Flue gas dilution of the.

Vas 24 hours. Ybefore its lactivity or selectivity has appreciablydeclined in VVregeneration step and operating temperatures,

couc- 7 catalyst which is deactivated only to a slight extentrejuvenation maybe eected in .a matter of S'or v10 minutes `whilewithagcatalyst which has been used a long period of Vtime and has beendeactivated .toV a greater extent the rejuvenation time may be l hoursor more, badly deactivated catalysts having been rejuvenated'for 4aslong It is preferred to` rejuvenate the catalyst which case effectiverejuvenation maybe obtained by Contact with oxygen having a partialpressure of about 1 to 4 atmospheres at a temperature inthe range of 950to 1l00 F. for a time of about .rl to l0 hours, e. g. about V5 hours. j

When rejuvenation has been complete the catalyst must Y next bepurged'from oxygen before hydrogen is reiutroduced thereto. kThe oxygenpurge is effected by diff continuing'the introduction of air throughlines Strand- 66, introducing fuel Vgas by compresser Si, andopeuingvalvei7so that the oxygen in the circulating gas stream is all burned byintroduced fuel gas and gas is once more being cycled through thevcatalyst bed. During this oxygen purge step `the temperature of thecirculating gases mayA be lowered by heat exchanger 615 so that thereactor bed temperature is brought back` to conversion temperature whenrejuvenation is efected at 'a higher temperature. At the time of theoxygen purge it is preferred to reverse the flow ofthe gas streamthrough the reactor bed and this is accomplished simply by switching theposition of valves 72 and 7S so that gases from line '7l will flowthrough l-ines 79, 51 and 53- into the bottoni of vessel and gases fromthe top 'thereof owV through lines 458,. 46 andY 80 to discharge 75. Theoxygen purge may be discontinued when the lower part of the catalyst bedis at about reaction temperaturev even though the upper part of the bedis slightl' above reaction temperature. Y

After the oxygen purge is completed and the'circalaingV gas, now flowingfrom the bottorirto the top of thel reactor, is oxygen-free flue gasvalve-71a is closed andvalve 63a is opened, valve 53u closed and valvelais opened to purge the .flue gas out of the reactor with hot recyclehydrogen. This so-ealled hydrogen purge of flue gas is continued untilsubstantially all flue gas is.

If desiredthe purging steps may beeffectcd atreduced Y pressurebyopening valve 8in in line Si, which leads to vent line 78, landclosing Yvalve 76d. sential, however, that any of the operations beatreduced pressure and a pressure of at leastl 10Q p. s.- i. g. and preferablyeat lcastabout 200 p. s. i. g. is required for optimum reactionand rejuvenation, such pressure'being advantageous also for theregeneration step.

- The described arrangement of valves 72 and '75 'enables 'g simpleandexpeditious reversal 'of flow througl'i4 a catalyst While reactor 20 isori-stream the alten.

lt is not es-l charge attainable by a given amount of fresh catalyst atthe same temperature, pressure and charge rate, thc relative activity ofthe used catalyst is percent. Activity may also be defined byimprovement of octane number; i. e. a catalyst which converts a 45octane number naphth-a to a 95 octane number product is more active thanone which converts such naphtha to a product of only octane number underthe same operating conditions. Activity may also be measured by thetemperature required to produce a given octane number; a catalyst whichwill produce a octane numberproduct lat 92.0 F. is more active than acatalyst which requires 950 F. to produce the same octane number underthe same operating conditions-of pressure and space velocity and withthe same feed stock.

Selectivity of the catalyst is its property of limiting the conversionto dehydrogenation, aromatization and iso mcrization asopposed'tocracking, disproportionation and the formation of gas, cokeand higher boiling materials. A catalyst of high selectivity shouldproduce at least Yabout 90 percent by weight of C3-free 400 F. end pointgasoline from a charging stock as hereinabove defined. Withoutrejuvenation, a catalyst which has been used for a number of days(particularly in later cycles of operation) loses its ability to directthe conversion in the desired channely and results in formation of largeamounts of hydrocarbon gases, coke, polymer, etc. Loss in activity maybe balanced by use of higher temperatures and/ or lowcrrspace velocitybut loss of selectivityV inevitably means loss of valuable product. Thesystem hereinabove described is designed to notonly maintain thecatalyst athigh activity but also to prevent loss of selectivity duringcontinuousrepeated cycles of on-stream reaction, regeneration andrejuvenation. The plant operator can readily determine by thetemperature drop across each reactor and the'quality of thereactorefuent whether or not the activity and selectivity of thecatalyst therein has decreasedrto such-an extent that regeneration andrejuvenation are advisable. The length of on-stream runs in each reactorwill depend 'upon the'inature of the catalyst, the composition of thecharging stock, theVV severity of the treatment and othervariables but,generally speaking, a catalyst bed shouldl not remain oni-stream if itsrelative activity has dropped more than 50 percent or it' it ,be dilutedwithflue gasbut ordinarily a sufiiciently'high oxygen partialpressurecan be obtained by operating in Y theY manner hereinabovedescribed with chamber 59 serving the function of an air heater.

bed which is undergoing regeneration-rejuvenationY and/ or purgingsubstantially instantaneously and -as frequently.

as may be advantageous or desirable. The optimum method of operationWill'rbe somewhat dependen-t on `the amount'or" carbonaceous depositatobe hurnedin-the oxygen trations, but with the system herei bovedescribedyve are enabledV to attain maximum flexibility, n

As employed herein the ternractivity is the catalysts etc.

property .of `directing the'conver'sion to -a productof the desiredhiglroctane number in the range of about 90 to l0() at the definedtemperature, space velocity'and operating pressure; Relative activityhas reference V.to activ# From the foregoing description it Will beseen'that we ,have accomplished the objects of our invention and Whilewe have' illustrated the invention by a'speciiic example,

Y it shouldy be 'understood that alternative arrangements,

operating proceduresY and conditions will be apparent to those skilledin the art. Thus in this example the onstream conversion, regeneration,rejuvenation and purg-v ing steps are all effected at approximately 200p. s. i. g and Vit should be understood that the regeneration,rejuvenation and purging steps 'need not be at the same pressure as theconversion'step and that the-conversion step may befabove or below 200p. s. i. g. although it is preferablywithin therange of about to 35.0 p.s. i. g. In this example the ori-stream space velocity in each reactoris approximately 5 pounds'of liquid charge per hour'per pound ofcatalyst but this space velocity may range vfrom about 2` pounds5f-charge per hour to l0 pounds `per 44 A 444144.44MT 4 4 4444*4444 Ahour per pound of catalyst depending on the activity of p the particularcatalyst. The temperature at which charge enters the reactor may behigher or lower than 980 F. but is preferably in the range of about 950to 1000 F. The regeneration and rejuvenation steps may require more orless than the times hereinabove described but about 1 to hours is thepreferred range for each of these treatments. In some cases rejuvenationmay be effected at temperatures lower than 950 F. particularly with longcontact time and high oxygen partial pressure.

The reforming plant hereinabove described is designed to produce fromthe dened charging stock about 6.2 weight percent of hydrogen and C3 andlighter hydrocarbons, 92.4 weight percent of Ca-free 400 F. end pointhydroformate, 1.3 weight percent of higher boiling liquid product(usually called polymer) and less than .1 percent coke. Ofthe C3 'andlighter gases, about 90 mol percent is hydrogen and the remainder aboutequal mol percents of C1, C2 and C3 hydrocarbons. Of the hydroformateabout 2 percent is isobutane, 3 percent normal butane and 95 percentC5-400 F. gasoline having an API gravity of about 48.6, an F1 clearoctane number of about 93, an initialASTM boiling point of about 115 F.,10 percent point of 165 F., 50 percent point of 255 F. and 90 percentpoint of 340 F. The so-called polymer has an API gravity of about 11 andboils in the range of about 420 to 700 F. p

The product yield and octane number is, of course, somewhat dependent onthe charge employed `and the nature Vof the catalyst and the severity ofthe treatment. For example, a hydroformer charge boiling between about212 F. and 400 F.,'containing .03 weight percent sulfur and comprised ofabout 50 volume percent naphthenes, 36 volume percent parains, 13 volumepercent aromatics and 1 volume percent olefins, may yield undersubstantially the above defined conditions almost 15 percent C3 andlight-er gases, 81 percent C4-400 F. end point product gasoline andabout 4 percent polymer. The gasoline product in this case being a clearresearch octane number of approximately 100.

It should be understood, of course, that various other features may beincluded in the process design. Provision may be made in line 76 forremoving any catalyst fines which may be carried out of the reactorswith purged gas, regeneration gas, etc., cyclone separators, iilters orother separation means being effected for this purpose. SincetheV gasvelocity is greatest during the on-stream period, catalyst fines may becarried overhead with reaction products and recovered from the highboiling components thereof in any known manner. Provision may be madefor introducing into furnace 22 or 27 a charging stock which does notrequire the full three reactor system in which case, of course, thesefurnaces must be designed to provide the required heat for vaporizingand heating such extraneous stocks to the defined temperatures in therange of about 950 to 1000 F. The charging stock may be pre-fractionatedto insure removal of water, HzS and/ or components boiling above 400 F.end point and, if the charge has a high sulfur content, it may behydrodesulfurized or hydroiined in a conventional manner to lower itssulfur content arid/or remove any other impurities Which might bedetrimental to the platinum-on-alumina catalyst.

We claim:

1. A regenerative, platinum-catalyst, naphtha hydroforming system whichcomprises at least four reactors herein called alternate, first, secondand third reactors respectively, each adapted to contain a bed ofplatinum catalyst, a lower regeneration gas line, a connection includinga valve between the bottom of each reactor and said lower regenerationgas line, an upper regeneration gas line, a connection including a valvebetween the top of each reactor and the upper regeneration gas line, aregeneration system connected to said lower and upper regeneration gaslines, a charging stock heater, first re- 110 heater and second reheaterrespectively, an inlet at one end of each reactor Yand an outlet at theother end thereof, a charging stock heater discharge line alternatelyconnected by lines each containing a valve to discharge only to thealternate reactor and the rst reactor inlets, a rst reheater dischargeline connected by lines each containing a valve to discharge only to thealternate reactor and the second reactor inlets, a second reheaterdischarge line connected by lines each containing a valve to dischargeonly to the alternate reactor and the third reactor inlets, a firstreheater inletrline connected by lines each containing a valve toreceive eiuent from the outlets of only the alternate reactor andthefirst reactor, la second reheater inlet line connected by lines eachcontaining a valve to receive efuent from the outlets of only thealternate and second reactor, a gas separator having an inlet connectedby lines each containing a valve to receive effluent from the alternatereactor and the third reactor, whereby a naphtha charge ows in seriesthrough the heater, irst reactor, rst reheater, second reactor, secondreheater, and third reactor to the gas separator while catalyst in thealternate reactor is undergoing regeneration and whereby the alternatereactor may be connected in parallel with any selected one of the first,second and third reactors respectively and take the place thereof in anydesired sequence so that any selected reactor may be taken off streamfor regeneration without interrupting charging stock tlow'through thesystem or changing the order of said liow through the preheaters of thesystem.

2. The system of claim 1 which includes valve connections betweentheupper and lower regeneration gas lines and the regeneration systemwhereby the ow of gas through each reactor during regeneration may bealternated in direction.

3. The system of claim 1 wherein the regeneration system includes a gascooler, a gas circulator, a gas heater, connections for passing gas fromone of the regeneration gas lines through the cooler, compressor andheater to the other of said regeneration gas lines for establishing acirculating gas stream and a connection for introducing air into thecirculating gas stream.

4. A regenerative, "platinum-catalyst, naptha hydroforrning system whichcomprises at least four reactors, each containing a bed of such catalystand each having valved inlet lines and outlet lines of which at leastthree reactors are normally on stream and one is an alternate reactor,at least three heaters each having its respective transfer line,connecting lines for passing naphtha charging stock through the firstheater to the rst reactor inlet line, thence from the first reactoroutlet line through the second heater to the second reactor inlet line,thence fromA the second reactor outlet line, through the third heater tothe third reactor inlet line and thence from the third reactor o utletline ultimately to the inlet of a gas separator while catalyst in thealternate reactor is undergoing regeneration, and apparatus forsubstituting said alternate reactor for any selected one of theon-stream reactors whereby catalyst in the latter may undergoregeneration, which apparatus comprises a valved connection between thealternate reactor inlet line and each of said transfer lines, and valvedconnections between the alternate reactor ydischarge line and each ofthe other reactor outlet lines, whereby the naphtha continuously flowsin the same sequence through the three heaters and only the alternatereactor can be connected in parallel with or in place of any selectedone of the on-stream reactors.

5. The system of claim 4 which includes a regeneration gas heater, andconnecting lines and valves for passing an oxygen-containing gas throughsaid heater and thence through any selected one of said reactors whichis not connected in on-stream position.

6. The system of claim 5 which includes a valved connection forintroducing hot hydrogen into any selected reactor while no naphtha isbeing introduced thereto through the valved inlet thereof.

` 7. The system of claim 4 which includes a gas cooler, avgas heater, agas circulator, connecting lines and valves for circulating gas from oneend of a selected reactor through said cooler, heater and circulatorback to the other end thereof to form a circulating stream, a connectionfor introducing air into the circulating stream, and a connection forventing gas from the circulating stream.

8. The system of claim 4 which includes a product separator connected tothe last on-stream reactor, a recycle gas heater, a line for conveyinggas from the product separator to said recycle gas heater and aline forconveying heated gas from said recycle gas heater to the chargeintroduced to the first on-stream reactor.

9. A -regenerative platinum-catalyst naphtha hydroforming systemcontaining first, second, last and lalternate reactors respectively, apreheater, a first reheater, a last reheater, a product separator,connections for passing naphtha in series ow through the preheater,first reactor, first reheater, second reactor, last reheater, lastreactor and product separator, connections for introducing hydrogen fromthe separator to charge entering the first reactor, a connection fromthe transfer line of the last reheater for selectively passing itscontents to the alternate reactor, a connection from the alternatereactor for passing effluent therefrom to the product separator, thealternate reactor thus being connected in parallel with the vlastreactor, valves in theconnections entering and leaving the last reactorand the alternate reactor arranged so that all material from saidtransfer line can be passed through either one of said reactors and theother of said reactors can be isolated for regeneration, a gas cooler,compressor and heater, regeneration connections from one end of the lastand alternate reactors to said cooler and thence to said compressor andthence to said heater and Ithence to the other end of said reactorswhereby a regeneration gas stream may be circulated through the heaterand the reactor during regeneration, a connection for introducing airinto said stream whereby it may be heated; by said heater, saidregeneration connections containing valves for isolating one reactor forregeneration from the other reactor which is on-strearn whereby thealternate reactor may be substituted for the last reactor in the seriesflow betweenthe last reheater and the product separator when the lastreactor requires regeneration, the last reactor may be similarlysubstituted for the alternate reactor, and the last reactor and thealternate reactor may be operated in parallel.

10. The system of claim 9 which includes a valve connection between thetransfer line of the first reheater and the inlet of `the alternatereactor, a valve connection between the outlet of the alternate reactorand the outlet of the second reactor, and regeneration connections fromone end of the second reactor to said flue gas cooler, compressor andheater and from said flue gas heater to the other end of the secondreactor whereby the alternate reactor may be substituted for the secondreactor while the second reactor is undergoing regeneration.

11. The system of claim 9 which includes a valved connection forintroducing hydrogen at the charge inlet of each reactor at periods whenneither regeneration gases nor naphtha charging stock is introducedthereto.

l2. The system of claim 9 which includes a separate hydrogen heater as apart of the connections for introducing Ihydrogen from the separator tocharge entering the rst reactor.

13. In a platinum-catalyst, naphtha hydroforming process wherein anaphtha charge of low sulfur content is pre- 12 heated and introducedwithpreheated hydrogen to a first reaction zone, effluent from the firstzone is reheated and introduced into a second reaction Zone, efiuentfrom the secon-d zone is reheated and finally introduced into a lastreaction zone from which it is passed through a cooling zone to aseparation zone and Ihydrogen is recycled from the separation zonethrough a preheating zone for introduction to the first zone, theimproved method of operation which comprises periodically connecting anyselected reaction zone in parallel with an yalternate reaction Zone ofapproximately the same size as the first, second and last reaction zonesrespectively, each of the reaction zones containing a bed of supportedplatinum catalyst, blocking off the selected reaction zone to take itoff stream while the alternate zone takes its place in the on-streamsequence, purging hydrogen from the off-stream reaction zone, thenregenerating catalyst in the off-stream reactionV zone by burningcarbonaceous deposits therefrom with a gas having a low oxygen content,then purging oxygen from the off-stream zone land thereafter replacingthe purge gas with hydrogen, then placing the selected reaction zoneback von stream and thereafter taking the alternate reactor olf stream,and in the same manner replacing other of the first, second and lastreaction zones with the alternate reaction zone in any desired sequenceso that each of the reaction zones including the Ialternate may undergoregeneration While in off-stream position Without interrupting theron-stream flow and without changing the sequence of flow through thepreheating and the two reheating steps.

14. The method of claim 13 which includes the step of contacting thecatalyst in the off-stream zone after the regeneration step with a gasof higher oxygen content and heating said gas to a higher temperaturethan the oxygen content and inlet `temperature respectively of theregeneration'gas.

15. The method of claim 13 Whitch includes the step of generating fluegas for use in at least one of said purging steps, passing said flue gasthrough a cooler, compressor and heater for initial use, and passing apart of the combustion products produced in the regeneration stepthrough the cooler, compressor and heater to provide diluent gas duringat least a part of the regeneration step.

16. The method of claim 13 which includes the step of introducing into areaction zone in oli-stream position, after oxygen has been purgedtherefrom, a hydrogen gas from the separation zone which has been heatedto a lower temperature than the preheated hyd-rogen which is introducedinto the first reaction zone.

17. The method of claim 13 wherein the pressures in the on-streamreaction zones are within the range of about to 350 p. s. i. g.

References Cited in the tile of this patent UNITED STATES PATENTS2,253,486 Belchetz Aug. 19, 1941 2,310,244 Lassiat Feb. 9, 19432,366,372 Voorhees Jan. 2, 1945 2,367,365 Mun-day et al J an. 16, 19452,487,717 Maker et al Nov. 81949 2,488,033 Johnson Nov. 15, 19492,505,263 Trotter Apr. 25, 1950 2,573,149 Kassel Oct. 30, 1951 2,578,704Houdry Dec. 18, 1951 2,606,862 Keith Aug. 12, 1952 2,654,694 Berger etal. Oct. 6, 1953 2,664,404 Blatz et al. Dec. 29, 1953

1. A REGENERATIVE, PLATINUM-CATALYST, NAPHTHA HYDROFORMING SYSTEM WHICHCOMPRISES AT LEAST FOUR REACTORS HEREIN CALLED ALTERNATE, FIRST, SECONDAND THEIR REACTORS RESPECTIVELY, EACH ADAPTED TO CONTAIN A BED OFPLATINUM CATALYST, A LOWER REGENERATION GAS LINE, A CONNECTION INCLUDINGA VALVE BETWEEN THE BOTTOM OF EACH REACTOR AND SAID LOWER REGENERATIONGAS LINE, AN UPPER REGENERATION GAS LINE, A CONNECTION INCLUDING A VALVEBETWEEN THE TOP OF EACH REACTOR AND THE UPPER REGENERATION GAS LINE, AREGENERATION SYSTEM CONNECTED TO SAID LOWER AND UPPER REGENERATION GASLINES, A CHARGING STOCK HEATER, FIRST REHEATER AND SECOND REHEATERRESPECTIVELY, AN INLET AT ONE END OF EACH REACTOR AND AN OUTLET AT THEOTHER END THEREOF, A CHARGING STOCK HEATER DISCHARGE LINE ALTERNATELYCONNECTED BY LINES EACH CONTAINING A VALVE TO DISCHARGE ONLY TO THEALTERNATE REACTOR AND THE FIRST REACTOR INLETS, A FIRST REHEATERDISCHARGE LINE CONNECTED BY LINES EACH CONTAINING A VALVE TO DISCHARGEONLY TO THE ALTERNATE REACTOR AND THE SECOND REACTOR INLETS, A SECONDREHEATER DISCHARGE LINE CONNECTED BY LINES EACH CONTAINING A VALVE TODISCHARGE ONLY TO THE ALTERNATE REACTOR AND THE THIRD REACTOR INLETS, AFIRST REHEATER INLET LINE CONNECTED BY LINES EACH CONTAINING A VALVE TORECEIVE EFFLUENT FROM THE OUTLETS BY ONLY THE ALTERNATE REACTOR AND THEFIRST REACTOR, A SECOND REHEATER INLET LINE CONNECTED BY LINES EACHCONTAINING A VALVE TO RECEIVE EFFLUENT FROM THE OUTLETS OF ONLY THEALTERNATE AND SECOND REACTOR, A GAS SEPARATOR HAVING AN INLET CONNECTEDBY LINES EACH CONTAING A VALVE TO RECEIVE EFFLUENT FROM THE ALTERNATEREACTOR AND THE THIRD REACTOR, WHEREBY A NAPHTHA CHARGE FLOWS IN SERIESTHROUGH THE HEATER, FIRST REACTOR, FIRST REHEATER, SECOND REACTOR,SECOND REHEATER, AND THIRD REACTOR TO THE GAS SEPARATOR WHILE CATALYSTIN THE ALTERNATE REACTOR IS UNDERGOING REGENERATION AND WHEREBY THEALTERNATE REACTOR MAY BE CONNECTED IN PARALLEL WITH ANY SELECTED ONE OFTHE FIRST, SECOND AND THIRD REACTORS RESPECTIVELY AND TAKE THE PLACETHEREOF IN ANY DESIRED SEQUENCE SO THAT ANY SELECTED REACTOR MAY BETAKEN OFF STREAM FOR REGENERATION WITHOUT INTERRUPTING CHARGING STOCKFLOW THROUGH THE SYSTEM OR CHANGING THE ORDER OF SAID FLOW THROUGH THEPREHEATERS OF THE SYSTEM.
 13. IN A PLATINUM-CATALYST, NAPHTHAHYDROFORMING PROCESS WHEREIN A NAPHTHA CHARGE OF LOW SULFUR CONTENT ISPREHEATED AND INTRODUCED WITH PREHEATED HYDROGEN TO A FIRST REACTIONZONE, EFFLUENT FROM THE FIRST ZONE IS REHEATED AND INTRODUCED INTO ASECOND REACTION ZONE, EFFLUENT FROM THE SECOND ZONE IS REHEATED ANDFINALLY INTRODUCED INTO A LAST REACTION ZONE FROM WHICH IT IS PASSEDTHROUGH A COOLING ZONE TO A SEPARATION ZONE AND HYDROGEN IS RECYCLEDFROM THE SEPARATION ZONE THROUGH A PREHEATING ZONE FOR INTRODUCTION TOTHE FIRST ZONE, THE IMPROVED METHOD OF OPERATION WHICH COMPRISESPERIODICALLY CONNECTING ANY SELECTED REACTION ZONE IN PARALLEL WITH ANALTERNATE REACTION ZONE OF APPROXIMATELY THE SAME SIZE AS THE FIRST,SECOND AND LAST REACTION ZONES RESPECTIVELY, EACH OF THE REACTION ZONESCONTAINING A BED OF SUPPORTED PLATINUM CATALYST, BLOCKING OFF THESELECTED REACTION ZONE TO TAKE IT OFF STREAM WHILE THE ALTERNATE ZONETAKES ITS PLACE IN THE ON-STREAM SEQUENCE, PURGING HYDROGEN FROM THEOFF-STREAM REACTION ZONE, THEN REGENERATING CATALYST IN THE OFF-STREAMREACTION ZONE BY BURNING CARBONACEOUS DEPOSITS THEREFROM WITH A GASHAVING A LOW OXYGEN CONTENT, THEN PURGING OXYGEN FROM THE OFF-STREAMZONE AND THEREAFTER PLACING THE PURGE GAS WITH HYDROGEN, THEN PLACINGTHE SELECTED REACTION ZONE BACK ON STREAM AND THEREAFTER TAKING THEALTERNATE REACTOR OFF STREAM, AND IN THE SAME MANNER REPLACING OTHER OFTHE FIRST, SECOND AND LAST REACTION ZONES WITH THE ALTERNATE REACTIONZONE IN ANY DESIRED SEQUENCE SO THAT EACH OF THE REACTION ZONESINCLUDING THE ALTERNATE MAY UNDERGO REGENERATION WHILE IN OFF-STREAMPOSITION WITHOUT INTERRUPTING THE ON-STREAM FLOW AND WITHOUT CHANGINGTHE SEQUENCE OF FLOW THROUGH THE PREHEATING AND THE TWO REHEATING STEPS.